One of radiographic inspection apparatuses is a computed tomography (CT) apparatus. The CT apparatus comprises an X-ray tube for radiating X-ray fan beams, and a radiation detector comprising a large number of radiation detection elements. The X-ray tube and the radiation detector are arranged oppositely to each other with an object to be measured at center. X-ray fan beams radiated from the X-ray tube pass through the object to be measured, and are detected by the radiation detector. With every radiation having a changed angle, X-ray absorption data are collected to calculate X-ray absorbance at each position in each cross section of the object by computer analysis, thereby forming an image based on the X-ray absorbance. The radiation detection element is constituted by a large number of scintillator cells. The radiation detector includes a detector comprising scintillators and silicon photodiodes, or a detector comprising scintillators and photomultiplier tubes.
A dual-energy detector comprising two types of scintillators with different X-ray detection sensitivity distributions is disclosed, for example, by U.S. Pat. No. 4,511,799 and WO 2006/114715 (JP 2008-538966 A). U.S. Pat. No. 4,511,799 discloses a dual-energy detector in which light emitted from one scintillator is received by one diode, and light emitted from the other scintillator is received by the other diode, but fails to disclose a specific production method thereof. WO 2006/114715 also fails to specifically disclose the production method of a scintillation array.
JP 2002-236182 A (U.S. Pat. No. 6,793,857) discloses a method for producing a mono-dimensional or multi-dimensional detector array comprising scintillator cells with different widths. This method comprises (a) forming a composite layer comprising a sensor layer made of a material sensitive to radiation and a substrate layer, and (b) cutting the material of the composite layer from the opposite side to the substrate layer to divide the sensor layer to individual insulated elements, thereby forming partition walls in the sensor layer. However, this method suffers increase in the number of steps as the number of cells increases, resulting in lower assembly precision.
JP 2001-174564 A discloses an X-ray detector array comprising two types of scintillators elements arranged in an X-ray transmission direction for detecting X-rays with different energy distributions, a light-detecting element for each scintillator element being arranged in a direction perpendicular to the scintillator element, and pluralities of scintillator elements and pluralities of light-detecting elements being aligned in lines. Pluralities of scintillator elements are integrally molded with a light-reflective material. However, JP 2001-174564 A does not specifically disclose the production method of the X-ray detector array.
JP 2009-524015 A discloses a method for producing a scintillation array, which comprises producing a scintillation ceramic wafer, forming pluralities of slits on an upper surface of the ceramic wafer in two perpendicular directions, and oxidizing part of the ceramic wafer surface to form a reflection layer. Slits for gaps between individual pixels are also filled with the reflection layer. However, this scintillation array is formed by one type of scintillation ceramic. Thus, JP 2009-524015 A neither discloses nor suggests the technology of arranging two types of scintillation cells with high precision.